Willwood Formation facts for kids
Quick facts for kids Willwood FormationStratigraphic range: Thanetian-Ypresian (Clarkforkian-Bridgerian) ~56–48Ma |
|
|---|---|
| Type | Geological formation |
| Sub-units | Gray Bull beds, Sand Coulee beds, Sand Creek Facies, Wa-1 Zone |
| Lithology | |
| Primary | Mudstone, shale |
| Other | Sandstone, conglomerate |
| Location | |
| Coordinates | 44°30′N 108°00′W / 44.5°N 108.0°W |
| Approximate paleocoordinates | 49°12′N 90°48′W / 49.2°N 90.8°W |
| Region |  Wyoming |
| Country |  USA |
| Extent | Bighorn Basin |
| Type section | |
| Named for | Shale, mudstone, limestone |
The Willwood Formation is a sedimentary sequence deposited during the late Paleocene to early Eocene, or Clarkforkian, Wasatchian and Bridgerian in the NALMA classification.
Description
It consists of fine grained clastic rocks (mudstone and shale) interbedded with medium grained clastic rocks (sandstone) and sporadic conglomerates. The formation underlies portions of the Bighorn Basin of Big Horn, Hot Springs, Park and Washakie counties of Wyoming.
Dating
Radiometric dating of volcanic tuffs, combined with comparisons with other formations using magnetostratigraphy, using numerous samples from various levels of the formation suggest an age range of 55 - 52 million years ago, placing the Paleocene-Eocene boundary near the base of the formation.
Fossil content
Trace fossils have been found in the Willwood Formation. Fossil birds include Gastornis, Neocathartes and Paracathartes. A fossil alligatorid, namely Orthogenysuchus, was also found in this formation.
Wasatchian correlations
| Formation | Wasatch | DeBeque | Claron | Indian Meadows | Pass Peak | Tatman | Willwood | Golden Valley | Coldwater | Allenby | Kamloops | Ootsa Lake | Margaret | Nanjemoy | Hatchetigbee | Tetas de Cabra | Hannold Hill | Coalmont | Cuchara | Galisteo | San Jose | Ypresian (IUCS) • Itaboraian (SALMA) Bumbanian (ALMA) • Mangaorapan (NZ) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Basin | Powder River Uinta Piceance Colorado Plateau Wind River Green River Bighorn |
Piceance |
Colorado Plateau |
Wind River |
Green River |
Bighorn |
Williston | Okanagan | Princeton | Buck Creek | Nechako | Sverdrup | Potomac | GoM | Laguna Salada | Rio Grande | North Park | Raton | Galisteo | San Juan | ||
| Country | United States |
 Canada |
United States |
 Mexico |
United States |
|||||||||||||||||
| Copelemur |  |
|
|
|
||||||||||||||||||
| Coryphodon | |
|
|
|
|
|
|
|
|
|
||||||||||||
| Diacodexis | |
|
|
|
|
|
|
|||||||||||||||
| Homogalax | |
|
|
|
|
|
|
|||||||||||||||
| Oxyaena | |
|
|
|
|
|||||||||||||||||
| Paramys | |
|
|
|
|
|
|
|
|
|||||||||||||
| Primates |  |
|
|
|
|
|
|
|||||||||||||||
| Birds |  |
|
|
|
|
|||||||||||||||||
| Reptiles |  |
|
|
|
|
|
|
|||||||||||||||
| Fish |  |
|
|
|
|
|
|
|||||||||||||||
| Insects |  |
|
|
|
|
|
||||||||||||||||
| Flora |  |
|
|
|
|
|
|
|
|
|||||||||||||
| Environments | Alluvial-fluvio-lacustrine | Fluvial | Fluvial | Fluvio-lacustrine | Fluvial | Lacustrine | Fluvio-lacustrine | Deltaic-paludal | Shallow marine | Fluvial | Shallow marine | Fluvial | Fluvial |
 Wasatchian volcanoclastics Wasatchian fauna Wasatchian flora |
||||||||
| Volcanic | Yes | No | Yes | No | Yes | No | Yes | No | Yes | No | ||||||||||||
